JP4520222B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a resampling processing technique for a data string.

  In general, reception data handled by an ultrasonic diagnostic apparatus has a larger number of samples than the number of display pixels on a monitor screen on which an ultrasonic image is projected. That is, the sampling frequency of received data is higher than the sampling frequency of display pixel data. For this reason, frequency conversion processing from the sampling frequency of received data to the sampling frequency of display pixel data is performed in the course of data processing in the ultrasonic diagnostic apparatus (for example, Patent Document 1). The frequency conversion is realized by a thinning process that extracts some data from the received data string at predetermined intervals.

  When the sampling frequency is converted by this thinning process, an anti-aliasing filter (anti-aliasing filter) is required to prevent aliasing distortion of high-frequency components after the thinning process. That is, before performing the thinning process, it is necessary to perform the thinning process after removing high-frequency components in advance by an anti-aliasing filter configured by an FIR (Finite Impulse Response) filter or the like.

  FIG. 7 is a diagram for explaining a resampling process that is generally performed. The input data string 70 to be subjected to frequency conversion is, for example, an echo data string. Each data (0, 1, 2,...) Of the input data string 70 is subjected to anti-aliasing processing by an N-tap FIR filter. That is, the filter coefficient window 72 composed of N coefficients sequentially filters the input data while shifting each data of the input data string 70 by one sample. For example, data 0 of the filter output 74 is generated from N data of input data 0 to N−1, and data 1 of the filter output 74 is generated from N data of input data 1 to N. The coefficient of the FIR filter is set so as to remove the high frequency component, and as a result, the filter output 74 is output to the memory as a data string obtained by removing the high frequency component from the input data string 70. Then, each data of the filter output 74 stored in the memory is sequentially read out, and data is extracted at a predetermined interval, whereby data 76 after thinning is formed.

Japanese Patent Publication No. 8-4591 Japanese Patent Laid-Open No. 10-319059

  As described above, in the conventional resampling process, the thinning process is performed after the anti-aliasing process. For this reason, in the conventional ultrasonic diagnostic apparatus, the anti-aliasing filter and the thinning circuit are separately provided.For example, the data string after the anti-aliasing process is temporarily stored in the memory, and the thinning process is performed on the data string read from the memory. After application, the circuit configuration is redundant, such as storing in another memory again.

  Therefore, an object of the present invention is to provide an improved configuration for realizing the resampling process.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes a transmission / reception unit that transmits and receives ultrasonic waves to acquire an echo data sequence, and performs signal processing on the echo data sequence. An echo data processing unit that generates a display pixel data sequence; and a display unit that displays an ultrasound image corresponding to the display pixel data sequence, wherein the echo data processing unit is an input corresponding to the echo data sequence. An FIR filter that generates an output data string corresponding to the display pixel data string by performing data thinning processing and anti-aliasing processing on the data string, and the FIR filter includes a plurality of windows in a window set in the input data string. Output data is generated from input data, and output data is generated sequentially while shifting the window in steps according to the data decimation rate. The features.

  In this configuration, the echo data processing unit generates display pixel data from the echo data by using a conventionally known technique such as detection processing, tomographic image formation processing, Doppler image formation processing, display image formation processing, and the like. The echo data processing unit executes resampling processing (resampling processing) which is one of the features of the present invention. The resampling process includes a data thinning process and a loopback prevention process, and the FIR filter in the above configuration can simultaneously execute these two processes.

  That is, the coefficient of the FIR filter is set so as to remove the high frequency component that causes the aliasing distortion, thereby realizing the aliasing prevention function. Further, a window for cutting out a plurality of input data is sequentially set according to the data decimation rate, for example, while skipping a predetermined number of input data, and thereby, output data is sequentially formed so that a data decimation function is realized. .

  When the resampling process is configured by hardware with the above configuration, a memory and a buffer for storing the data after the anti-aliasing process that is necessary in the conventional hardware configuration are not necessary. Further, when the resampling process with the above configuration is realized as a software function using a CPU or a DSP (digital signal processor), the anti-aliasing process is not performed on the extra data discarded by the decimation process. Since the anti-aliasing process can be executed only for the valid data extracted by the above, the load of the anti-aliasing process is reduced.

  The thinning rate can be determined by the ratio of the number of samples of echo data and the number of samples of display pixel data, and the coefficient of the FIR filter can be uniquely determined with respect to the thinning rate. System design becomes easy.

  Preferably, a window setting unit that cumulatively adds data thinning rates each time each input data constituting the input data string is acquired, and outputs a window setting pulse every time the addition result exceeds a predetermined value. And setting a window in the input data string in accordance with an output timing of the window setting pulse. Preferably, the FIR filter is provided in a detection unit included in the echo data processing unit. Preferably, the FIR filter is provided in an image construction unit included in an echo data processing unit.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes a transmission / reception unit that transmits and receives ultrasonic waves to acquire an echo data sequence, and performs signal processing on the echo data sequence. An echo data processing unit that generates a display pixel data sequence and a display unit that displays an ultrasound image corresponding to the display pixel data sequence, the echo data processing unit corresponding to the echo data sequence A data processing module that performs a resampling process on the input data string to generate an output data string corresponding to the display pixel data string, and the data processing module extracts a predetermined number of input data from the input data string Each input data extracted in this step is multiplied by a coefficient, and a process for generating output data by adding a predetermined number of multiplied input data is executed. Run while sequentially selected in accordance with input data of a predetermined number in the data thinning ratio that, characterized in that.

  Preferably, the coefficient multiplied to each input data is determined based on at least one of an ultrasonic transmission frequency and a diagnostic depth.

  The present invention provides a new configuration for realizing the resampling process. According to the present invention, since the data thinning process and the anti-aliasing process can be executed simultaneously, for example, the circuit configuration is simplified and the processing load of the anti-aliasing process is reduced.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is an overall configuration diagram thereof.

  The array probe 10 is an ultrasonic probe that transmits ultrasonic waves into a living body (not shown) and acquires echo data from the living body. The array probe 10 has a plurality of vibration elements, and the transmission timing of ultrasonic pulses output from each vibration element is controlled as appropriate, and scanning of an ultrasonic beam by an electronic scanning method is realized. The Examples of the electronic scanning method include linear scanning and sector scanning.

  The transmission unit 12 supplies a transmission signal to the array probe 10. The transmission signal is generated based on electronic scanning control by the transmission beam former 14. The receiving unit 16 acquires echo data for each vibration element output from the array probe 10, and the reception beamformer 18 amplifies and arranges a plurality of echo data corresponding to the plurality of vibration elements. Perform processing such as phase addition. The transmission beamformer 14 and the reception beamformer 18 steer the ultrasonic beam to form a scanning surface for transmitting and receiving waves. As a result, a plurality of echo data for each ultrasonic beam in the scanning surface are received from the reception beamformer 18. (Echo data after phasing addition) is output as an echo data string.

  The echo data sequence output from the reception beamformer 18 is orthogonally detected by the orthogonal detector 20 and output to the beam data processor 22 and the color Doppler processor 24.

  The beam data processing unit 22 forms so-called B-mode image data based on the echo data string after detection. A well-known technique is used for the B-mode image forming process, and pixel values corresponding to the magnitude of the amplitude are assigned to each echo data to form image data. The formed image data is output to the image construction unit 26.

  The color Doppler calculation unit 24 forms a so-called color Doppler image based on the echo data after detection. A well-known technique is used for the color Doppler image forming process. That is, for example, velocity information is extracted from echo data corresponding to blood flow and the like, and a color Doppler image is formed on the tomographic image by performing coloring processing corresponding to the velocity for each part in the blood flow. The image data of the formed color Doppler image is output to the image construction unit 26.

  For example, based on a user operation, the image construction unit 26 selects either the B-mode image or the color Doppler image as a display image and causes the display unit 28 to display the selected image. Of course, a display image in which a B-mode image and a color Doppler image are displayed at the same time may be formed according to a user request.

  In the present embodiment, resampling processing is performed from the sampling frequency of received data to the sampling frequency of display pixel data. This resampling process is executed in the quadrature detection unit 20 or the image construction unit 26.

  FIG. 2 is a diagram showing an internal configuration of the quadrature detection unit (reference numeral 20 in FIG. 1). In the following description, the parts shown in FIG. The echo data string output from the reception beamformer 18 is input to the two multipliers 30. One of the two multipliers 30 corresponds to the in-phase component, and the other corresponds to the quadrature component. The outputs of the two multipliers 30 are output to the corresponding FIR filters 32, respectively. Each FIR filter 32 functions as a low-pass filter that removes high-frequency components from the output signal of the multiplier 30 and extracts modulated signals of in-phase components and quadrature components.

  When the resampling process is executed by the quadrature detection unit 20, the process is executed in each FIR filter 32. That is, the FIR filter 32 performs an anti-aliasing process and a thinning process using the echo data string immediately after detection as an input data string, and generates an output data string corresponding to the display pixel data string. The resampling process will be described in detail later using FIG.

  FIG. 3 is a diagram illustrating an internal configuration of the image configuration unit (reference numeral 26 in FIG. 1). In the following description, the parts shown in FIG. When the resampling process is executed in the image construction unit 26, the process is executed in the FIR filter 32 arranged in the first stage of the image construction unit 26. That is, the FIR filter 32 performs an anti-aliasing process and a thinning process using the image data sequence corresponding to the sampling frequency of the echo data sequence output from the beam data processing unit 22 or the color Doppler calculation unit 24 as an input data sequence, An output data string corresponding to the pixel data string is generated. The resampling process will be described later in detail with reference to FIG.

  The data string after frequency conversion output from the FIR filter 32 is converted into a pixel data string for a display image by the image processing unit 34 and converted into a scanning method corresponding to the display unit 28 by the digital scan converter (DSC) 36. The

  FIG. 4 is a diagram for explaining the resampling process in the present embodiment. As described above, in the present embodiment, the resampling process is performed in the FIR filter of the quadrature detection unit (reference numeral 20 in FIGS. 1 and 2) or the image construction part (reference numeral 26 in FIGS. 1 and 3). In any case, the data thinning process and the aliasing prevention process are performed on the input data string 40 corresponding to the echo data string, and the output data string 44 corresponding to the display pixel data string is generated.

  Each data (0, 1, 2,...) Of the input data string 40 is processed by an N-tap FIR filter. That is, the filter coefficient window 42 including N coefficients (c0, c1, c2,...) Cuts out N pieces of input data from the input data string 40, and a coefficient is added to each of the cut out pieces of N input data. Multiply Then, the output data is generated by adding the N input data after multiplication. For example, data 0 of a data string (output data string) 44 after filtering is generated from N data of input data 0 to N−1, and the output data string 44 of N data of input data 2 to N + 1 is generated. Data 2 is generated.

  At this time, the filter coefficient window 42 is shifted in step 46 according to the data thinning rate. Step 46 in FIG. 4 corresponds to a data thinning rate of 0.5. That is, first, a window starting from the input data 0 of the input data string 40 is set, and then a window starting from the input data 2 is set by skipping the input data 1. In this way, output data obtained from a window starting from input data 0, output data obtained from a window starting from input data 2, output data obtained from a window starting from input data 4,... Then, output data is acquired one after another while skipping input data one by one. As a result, the thinning process is executed at a rate of one output data for every two pieces of input data, that is, at a data thinning rate of 0.5.

  Further, the coefficients (c0, c1, c2,...) Of the FIR filter multiplied by each input data prevent aliasing distortion of high frequency components after the thinning process, that is, remove high frequency components. Is set. Therefore, by sequentially generating output data while shifting the window in step 46 according to the data thinning rate, the data thinning process and the anti-aliasing process are performed simultaneously.

  FIG. 5 shows an adder 50 that outputs a window setting pulse. The adder 50 is provided, for example, as a function in a control unit (not shown) that controls the operation of each unit in the ultrasonic diagnostic apparatus.

  The adder 50 functions as a window setting unit that outputs a window setting pulse 54 based on the thinning rate. The decimation rate is calculated based on the ratio between the number of samples of the input data string before frequency conversion input to the FIR filter and the number of samples of the output data string after frequency conversion output from the FIR filter. / Number of input samples ”. In general, in the ultrasonic diagnostic apparatus, the number of samples in the output data string corresponding to the display pixel data string is smaller than the number of samples in the input data string corresponding to the echo data string, and therefore the value of the thinning rate is 1 or less. . In FIG. 5, the processing operation of the adder 50 will be described by taking a case where the thinning rate is “0.6” as an example.

  The adder 50 cumulatively adds the thinning rate each time input data is input into the FIR filter that executes resampling processing, and outputs the window setting pulse 54 every time the addition result becomes a predetermined value “1” or more. Output. The addition value 52 indicates a cumulative addition result of the thinning rate. That is, first, the thinning rate “0.6” is added to the initial value “0”, and the addition result “0.6” becomes the added value 52. Further, the thinning rate “0.6” is added to the addition value “0.6” at the next input data acquisition timing, and the addition result becomes “1.2”. However, when the addition result is 1 or more, the window setting pulse 54 becomes “H”, and the value “0.2” below the decimal point of the addition result is used as the addition value 52. Further, the thinning rate “0.6” is added to the added value “0.2” to obtain an addition result “0.8”. In this case, since the addition result does not exceed 1, the window setting pulse 54 becomes “L”. In this way, the window setting pulse 54 is set to “H” every time the addition result becomes 1 or more.

  The FIR filter (reference numeral 32 in FIGS. 2 and 3) uses the window setting pulse 54 as a write signal 56 of the filter output. That is, a filter coefficient window (reference numeral 42 in FIG. 4) is set with the input data acquired when the filter output write signal 56 becomes “H” as the head, and the output data acquired from the set window is Write to memory. Note that the input data read address 58 indicates the input data at the head of the window in the input data string 40. As described above, the FIR filter executes the filtering process only when the write signal 56 of the filter output is “H”, that is, only when the window setting pulse 54 is “H”.

数１において、data[]は入力データ、coef[]はフィルタ係数、out[]は出力データである。また、addr_iは入力データの読み出しアドレス（図５の符号５８）であり、TAPはＦＩＲフィルタのタップ数に相当する。数１に基づいて、例えば、ＣＰＵやＤＳＰなどのプロセッサを利用することにより、本実施形態におけるＦＩＲフィルタの機能をソフトウェアで構成することができる。 The function of the FIR filter described with reference to FIGS. 4 and 5 can be expressed by the following mathematical formula.

In Equation 1, data [] is input data, coef [] is a filter coefficient, and out [] is output data. Further, addr _i is a read address of the input data (code 58 in FIG. 5), TAP is equivalent to the number of taps of the FIR filter. Based on Equation 1, for example, by using a processor such as a CPU or DSP, the function of the FIR filter in this embodiment can be configured by software.

  The filter coefficient of the FIR filter that executes the resampling process depends on the thinning rate, and the thinning rate depends on the sampling frequency of the input data string of the FIR filter. For this reason, it is preferable to switch the FIR filter coefficient in accordance with the number of received samples (the number of echo data samples) determined by the ultrasonic transmission frequency and the diagnostic range (transmission / reception wave depth).

FIG. 6 shows the filter characteristics of the FIR filter, with the horizontal axis representing frequency (freq) and the vertical axis representing power (dB). The cutoff frequency of the filter is set according to the thinning rate. That is, the cutoff frequency is increased when the value of the thinning rate is large, and the cutoff frequency is decreased when the value of the thinning rate is small. In the present embodiment, filter characteristics (filter coefficients) are appropriately controlled according to the thinning rate to prevent aliasing. In addition, the ideal cut-off frequency can be expressed as "thinning rate × f _{s /} 2". Here, f _s is the sampling frequency of the input data string of the filter.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

1 is an overall configuration diagram of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows the internal structure of a quadrature detection part. It is a figure which shows the internal structure of an image structure part. It is a figure for demonstrating a resampling process. It is a figure which shows the adder which outputs a window setting pulse. It is a figure which shows the filter characteristic of a FIR filter. It is a figure for demonstrating the conventional resampling process.

Explanation of symbols

  20 quadrature detection unit, 26 image configuration unit, 32 FIR filter, 40 input data string, 42 filter coefficient window, 44 output data string.

Claims (5)

A transmission / reception unit for transmitting and receiving ultrasonic waves to acquire an echo data string;
An echo data processing unit that performs signal processing on the echo data sequence to generate a display pixel data sequence;
A display unit for displaying an ultrasonic image corresponding to the display pixel data string;
Have
The echo data processing unit includes an FIR (Finite Impulse Response) filter that generates an output data sequence corresponding to the display pixel data sequence by performing data thinning processing and anti-aliasing processing on the input data sequence corresponding to the echo data sequence. Including
The FIR filter generates output data from a plurality of input data in a window set in the input data string, sequentially generates output data while shifting the window in steps according to a data thinning rate ,
A window setting unit that cumulatively adds a data thinning rate every time each input data constituting the input data string is acquired, and outputs a window setting pulse every time the addition result becomes a predetermined value or more,
Setting a window in the input data string according to the output timing of the window setting pulse;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The FIR filter is provided in a detection unit included in an echo data processing unit.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The FIR filter is provided in an image configuration unit included in an echo data processing unit.
An ultrasonic diagnostic apparatus. A transmission / reception unit for transmitting and receiving ultrasonic waves to acquire an echo data string;
An echo data processing unit that performs signal processing on the echo data sequence to generate a display pixel data sequence;
A display unit for displaying an ultrasonic image corresponding to the display pixel data string;
Have
The echo data processing unit includes a data processing module that generates an output data sequence corresponding to the display pixel data sequence by performing a resampling process on an input data sequence corresponding to the echo data sequence,
The data processing module extracts a predetermined number of input data within the window set in the input data string , multiplies each extracted input data by a coefficient, adds the predetermined number of multiplied input data, and outputs the result Execute the process to generate data, and execute this process sequentially while shifting the window in steps according to the data decimation rate,
A window setting unit that cumulatively adds a data thinning rate every time each input data constituting the input data string is acquired, and outputs a window setting pulse every time the addition result becomes a predetermined value or more,
Setting a window in the input data string according to the output timing of the window setting pulse;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 4 ,
A coefficient to be multiplied with each input data is determined based on at least one of an ultrasonic transmission frequency and a diagnostic depth.
An ultrasonic diagnostic apparatus.

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